Field of the Invention
The invention relates to a switching current source circuit, and more particularly to a fast switching current source circuit for providing a fast-switched output current.
Description of the Related Art
For a switching circuit, such as a switched-capacitor circuit, a bias current of operational amplifiers (OPAMPs) can be decreased at its sampling phase. A switched-capacitor circuit is a circuit that moves charges between different sampling capacitors in order to achieve a desired signal processing function. The switched-capacitor circuit can accurately implement the signal processing function based on ratios of capacitor sizes and a sampling rate. Switched-capacitor circuits are widely used to implement various circuit blocks such as sigma-delta analog-to-digital converters (ΣΔ ADCs), sigma-delta digital-to-analog converters (ΣΔ DACs), filters, decimators, etc.
If the bias current of the switching circuit is small or the loading of the bias current is heavy, the bias current requires a long settling time when the switching circuit is switching. In general, a higher bias current or a driving buffer is used to overcome the long settling time. However, extra static power consumption is increased.